The invention relates to a method for the production of shaped bodies from powders and/or granules, in particular of sorbent shaped bodies comprising micro- or mesoporous adsorbents and of composite adsorbents that are used to store useful heat and useful cold, by which vaporous materials are expelled from the sorbent shaped bodies by application of heat energy and can be condensed where it is appropriate. The materials that were vaporized will be adsorbed in gas phase on corresponding sorbent shaped bodies.
Sorbent shaped bodies can be coated, stacked or bundled to be used for adsorptive thermal energy storage with the help of, preferentially, water vapour. This can be used for instance in techniques of heating, and cooling/air conditioning, particularly by making use of natural thermal sources like terrestrial or solar heat. Possible applications of energy storage can exist everywhere where thermal energy must be available for temporary use periods, which should not happen to coincide with periods of heat generation or their accessibility. The economical scope of the application of sorbent shaped bodies, micro- or mesoporous sorbents, is to attain high space-time yields of the equipments by which the energy transformation, for instance that of heat storage, can be achieved. In this case, the external shape and the geometrical dimensions of the sorbent shaped bodies can be expediently adjusted to the corresponding equipment, for example, to the internal walls of the tube of heat accumulators.
According to the state of the art, silicate heat storage media is distinguished by micro- and mesoporous sorbents from which adsorbed water can be removed through heat without damage to their frameworks.
One can refer to the company's scripts “Baylith®—Information”, among them “80.100—general product description”, “81.503—Technical Properties” and “81.505—Features on technical application”, Bayer-Werke Leverkusen, as well as on “Zeosorb Molecular Sieves”, Chemie AG Bitterfeld Wolfen.
In the chemical technology, alumosilicate like zeolite that are subjected to catalytic modification processes are mainly employed for the achievement of high space-time yields (DE 44 33 120 A1). High heat storage can be gained through further modifications of such zeolite by exchanging the univalent cations in particular that of the first main group with multivalent cations preferably cations of the second main group. In the publication DE 33 12 875 A1, magnesium-containing zeolite granular materials are employed for the generation of useful heat and/or useful cold. Usual techniques employ appropriate activating components in a batch-process to achieve cation exchange for modification of silicate sorbents. According to another aspect of the state of the art, a deposition can be made to occur in a matrix of hydrophilic materials such as salt hydrates that are subjected to a reversible hydration. These are inert to temperature and are capable of sorption. Examples are given in DE 43 05 264 A1, in which calcium chloride is placed in a powder form zeolite (DE 43 05 264 A1) or in a silica gel (DE 197 34 887 A1). In the same way, the modification of pellets or pre-fabricated granular materials furnished with a binding agent can be possible.
As a general rule, synthetic sorbents adapted to intended functions, are available in a finely grained crystal form during generation thereof. Usually their crystal sizes do not exceed a maximum of 500 μm. However, to get effective heat storage in the apparatus, the bulk of crystals with defined gap volumes allow only limited flow-speeds of the vaporous materials. Conversely, sorbents shaped bodies that exhibit larger transport pores, cavities and fluidic tubes are already applied through which higher flow speeds of the vaporous materials are assured. The direct material and heat exchange process with respect to water vapour occurs in the pores of the sorbents.
The drawback of all of these model structures is that it is difficult to integrate the powder or the granule into shaped bodies, and therefore the granules must be fixed in the structure with an additional binding agent that is initially fluidic or pasty on a support. The binding agent remains a significant space-filling component of the shaped body that decreases the efficiency of the powders or granules particularly of the sorbents by locking the micropores.
The poor thermal conduction of the shaped bodies is also unfavourable, since they are made of insulating material mainly comprised of mineral components.
Shaped bodies with only lower firmness are attained by application of organic polymers as binding agents for activated charcoals like for instance that of phenol formaldehyde resins (GB 1 398 466 A), polyvinyl resins and polyacrylates. Polyurethane (U.S. Pat. No. 4,619,948 A, DE 35 10 209 A1) and lattices increase the firmness of shaped bodies only slightly. During the application of fluidic organic medias, the derivates of cellulose as matrix creators for activated charcoals and zeolite (GB 1 132 782 A, DE 30 22 008 A1, U.S. Pat. No. 4,742,040, DD of 206 330 B) will be at least soaked. The solidifying qualities of the binding agent are then perturbed.
Due to their higher temperature stability, inorganic binding agents that are resistant to deformation, such as, aluminium hydroxide hydrates, clays and silica gel, exhibit some advantages. By embedding the activated charcoals in silicic acid matrices (DE 30 15 439 A1) or aluminiumoxid hydrate matrices (U.S. Pat. No. 4,499,208) or bentonite (DE 15 67 491 A1) and special clays (metakaolinite; DE 33 12 639 A1), the binding agent locks the micropores of the adsorbent in high extent. Even during carbonation of a water-soluble pitch acid (DE 42 28 433 A1), the originated high stable and solid carbon matrix hinders those materials that are diffused in the micro- and meso-pores. As mentioned above, binding agent is ascribed to similar sorption qualities as the zeolite (DE 38 19 727 A1). However, an exclusion of a specific portion of sorption-active crystals during material or heat exchange processes as well as hindrance at inside and outside of the active-exchangeable surfaces during the exchange process will remain disadvantageous.
The use of already granulated or pelletized crystal's binding agent also leads to familiar disadvantages. Conversely, due to their larger geometric shapes there exist larger gap volumes which are advantageous for the fluidic guidance due to lower pressure loss. However, a permanent negative influence with regard to the material and heat conduction efficiency of the equipment is encountered. In this case granular materials binded with mineralized binding agents like silicic acid derivate or clays have advantages. These are sorption-active, and the binding agent negatively influences sorption ability of the granular materials only to a lower extent.
Furthermore there are sorbent shaped bodies known, which are provided with a fluid permeable wrappers made of ceramic or of metallic materials for a good material or energy exchange over the boundary walls (EP 0 140 380 A). In this case, the coating provides better structure stability against mechanical stress and overcomes some of the known drawbacks of the binding agents.
From the publication DE 42 38 878, it is known that the gas bubbles out of ceramic pouring-masses can be removed by the effect of a force field, for example through centrifugal equipment. In this way, hollow ceramic objects are produced in solid of revolution form. Models are applied that are soaked with a casting slip and pre-hardened thermally at low temperatures. However, an embedding of powders or granules in binding agents that can harden at low temperatures is not yet intended.
For heat storage by means of highly effective modified Alumo- and/or aluminum silicates, with lower hydrothermal stabilities, binding agents that harden under low temperatures are preferable without considerably decreasing the sorption ability. Although the desorption of the vaporous material in silicate storage media can occur desirably below 1000° C., for some active components of the sorbent shaped bodies approximately 200° C. temperature must be taken into account to get a complete desorption and a targeted higher cycle of restoration of the working capacity of the medium. The considerable loading alternations and the corresponding temperature change of about 150° C. has a durable influence on the long term binding ability of powders or granular materials into the sorbent shaped bodies. Therefore, structures of the porous sorbent support also must show a high stability. On the other hand, tensions due to temperature change are supposed to be intercepted from the stabilized walls for the sake of long stability of the shaped bodies.
Thus, the basic object of the invention is to eliminate the described drawbacks of the existing techniques.